The present invention relates to a piezo-electric/electrostrictive film type chip, which is an integrated body of piezo-electric/electrostrictive film type elements. More specifically, the present invention relates to a piezo-electric/electrostrictive film type chip which is suitably applicable to an ink-jet print head.
In recent years, as one of mechanisms for increasing a pressure in a pressurizing room formed in a substrate, a piezo-electric/electrostrictive film type element is known in which a volume of the pressurizing room is changed by a displacement of a piezo-electric/electrostrictive working portion formed on a wall of the pressurizing room. Such a piezo-electric/electrostrictive film type element has been used as an ink pump of a print head used for an ink-jet printer, or the like, which has a mechanism of supplying an ink into a pressurizing room and filling the pressurizing room with an ink, increasing a pressure of the pressurizing room by a displacement of a piezo-electric/electrostrictive working portion, thereby an ink fine powder is expelled from a nozzle hole connected to the pressurizing room so as to print letters.
FIG. 4 shows one embodiment of an ink-jet print head (one portion) in which the conventional and known piezo-electric/electrostrictive film type element is used as an actuator. The ink-jet print head was formed by unitarily connecting a piezo-electric/electrostrictive film type chip 10 consisting of a plurality of piezo-electric/electrostrictive actuators 20 and an ink nozzle member 11 having a plurality of nozzle holes 12 each corresponding to each of the plurality of piezo-electric/electrostrictive actuators 20. Ink supplied to pressurizing rooms 30 formed in piezo-electric/electrostrictive actuators 20 is expelled through nozzle holes 12 arranged in an ink nozzle member 11.
The ink nozzle member 11 includes a thin and plane nozzle plate 13 provided with a plurality of nozzle holes 12, a thin and plane orifice plate 15 provided with a plurality of orifice holes 14. The nozzle plate 13 and the orifice plate 15 are laminated so as to sandwich a flow path plate 16 and connected by an adhesive, or the like, so as to have a unitary structure. Inside the ink nozzle member 11, there are formed flow paths 17 for expelling ink which introduces the ink into nozzle holes 12 and flow paths 18 for supplying ink which introduces the ink into the orifice holes 14. Incidentally, the ink nozzle member 11 is usually made of plastic or metal.
The piezo-electric/electrostrictive actuator 20 includes a ceramic substrate 21 and a piezo-electric/electrostrictive working portion 22 unitarily formed in the ceramic substrate 21. The ceramic substrate 21 has a unitary structure in which a thin and plane closure plate 23 and a connecting plate 24 are laminated with a spacer plate 25 sandwiched therebetween. In the connecting plate 24 are formed a first through opening 26 and a second through opening 27 each corresponding to an orifice hole 14 formed in the orifice plate 15 of the ink nozzle member 11.
In the spacer plate 25 are formed a plurality of window portions 28. The spacer plate 25 is laminated on the connecting plate 24 so that the first through opening 26 and the second through opening 27 arranged in the connecting plate 24 correspond to each of the window portions 28. On the other side of the spacer plate 25 opposite to the side of the connecting plate 24, the closure plate 23 is superposed, and the openings of the window portions 28 are closed by the closure plate 23.
Thus, pressurizing rooms 30 are formed in the ceramic substrate 21.
On the outer surface of the closure plate 23 of the ceramic substrate 21, each of the piezo-electric/electrostrictive working portion 22 is arranged on positions corresponding to each of the pressurizing rooms 30. Here, the piezo-electric/electrostrictive working portion 22 consists of a lower electrode 31, a piezo-electric/electrostrictive layer 32, and an upper electrode 33.
An ink-jet print head is formed by unitarily connecting a piezo-electric/electrostrictive film type chip 10 and an ink nozzle member 11. When an ink-jet print head is unitarily formed, throughholes such as the first through opening 26 and the second through opening 27 formed in the piezo-electric/electrostrictive actuator 20 and throughholes such as a plurality of orifice holes 14 in an ink nozzle member 11 should keep a relation of accurate positions.
In such a unitary connection of the piezo-electric/electrostrictive film type chip 10 and the ink nozzle member 11, a pin hole 42 has been conventionally formed around an edge portion of the piezo-electric/electrostrictive film type chip 10 as shown in FIG. 5. A constructing pin (not shown) is inserted to the pin hole 42 for an absolute positioning so as to connect the piezo-electric/electrostrictive film type chip 10 to the ink nozzle member 11. Incidentally, 43 denotes an auxiliary hole into which an auxiliary pin (not shown) is inserted so as to avoid rotational slippage between the piezoelectric/electrostrictive film type chip 10 and the ink nozzle member 11.
However, demands of improving resolution and printing speed ability of an ink-Jet printer have been further increasing in recent years. As a result, as the degree of integration of a piezo-electric/electrostrictive film type chip 10 is increased, many nozzles are required. Along with the demand, enlargement of a piezo-electric/electrostrictive film type chip 10 has been further required. According to the enlargement of a piezoelectric/electrostrictive film type chip 10, a problem has arisen because the preciseness of positions of the pin hole 42 and a throughhole of the piezo-electric/electrostrictive actuator 20 deteriorates because the distance between the pin hole 42 and, the piezo-electric/electrostrictive actuator 20 located furthermost from the pin hole 42 is elongated when the pin hole 42 is formed in the edge portion of a piezo-electric/electrostrictive film type chip 10. This is because a ceramic substrate 21 is formed by a method including the steps of molding a ceramic green sheet, punching, laminating, unitarily firing, and therefore, a firing shrinkage of about 20% of a ceramic varies depending on the parts, which makes an absolute value of a variance large as the piezo-electric/electrostrictive film type chip 10 is enlarged.
Therefore, an object of the present invention is to provide a piezo-electric/electrostrictive film type chip, in which deterioration of preciseness of positions of a pin hole and a throughhole of a piezo-electric/electrostrictive actuator is minimized and which can be precisely connected with an ink nozzle member.
That is to say, according to the present invention, there is provided a piezo-electric/electrostrictive film type chip comprising:
a ceramic substrate having a spacer plate having a windows-disposed pattern comprising at least a plurality of window portions and a thin closure plate for closing the window portions that is unitarily connected with the spacer plate; and
a piezo-electric/electrostrictive working portion having a lower electrode, a piezo-electric/electrostrictive layer, and an upper electrode, each being formed in the form of a layer and laminated in this order at a closure portion of the window on the outer surface of the closure plate by a film formation method;
wherein a pin hole for positioning is formed in or near the center of gravity of the windows-disposed pattern.
A shortest distance A between window portions of the spacer plate and a pin hole for positioning preferably satisfies the formula 0.5xc3x97txe2x89xa6A (t: thickness of the spacer plate). In this case, t is preferably 0.5 mm or less.
Incidentally, a spacer plate is not a green sheet but a virtual portion specified by drawing a virtual line on a completed piezo-electric electrostrictive film type chip as shown in FIG. 4.